Abstract

Stormwater ponds now comprise a significant portion of standing water in urban areas. These ponds act to sequester excess run-off and pollutants, such as road salt deicers. While these man-made ponds are not intended to serve as freshwater ecosystems, it is becoming clear that they do provide habitat for many organisms, but we know little of their ecosystem structure, function and interactions with pollutants. From April through June 2009, we surveyed 8 stormwater ponds in the Red Run Watershed, Baltimore County, Maryland, USA to describe patterns in aquatic food webs associated with a gradient in road salt inputs. Periphyton, phytoplankton and zooplankton samples were collected from each pond every 4–6 weeks. Specific conductance, a measure of chloride salt loading, among the 8 ponds varied widely throughout the survey, ranging from 99 μS cm−1 to 19,320 μS cm−1. Low (average = 404 +/− 82.6 (SE) μS cm−1) and medium (average = 1749 +/− 267 (SE) μS cm−1) conductance ponds had lower algal biomass and higher densities of zooplankton taxa relative to high (average = 7231 +/− 2143 (SE) μS cm−1) conductance ponds, which were largely devoid of all zooplankton through the end of May. The observed decline in zooplankton density along an increasing chloride gradient is consistent with experimental results of road deicer effects, suggesting algal resources are possibly freed from grazing pressure as zooplankton consumers are negatively impacted by road salt exposure. Our results highlight the potential for both direct and indirect effects of road deicers on freshwater communities.

Keywords

Notes

Acknowledgements

We thank Matt Gallagher and Adrianne Brand for their efforts in indentifying and initial surveying of the stormwater ponds used in this study. Many hours of field and laboratory assistance were given by Catie Iacovino, Saliha Khan, Bob Greisbach, Chance Pascale and Dan Miles. We gratefully acknowledge support from the US National Science Foundation (NSF), Long-Term Ecological Research (DEB-0423476) and Integrated Graduate Education Research and Training programs (NSF award #0549469), and the US Geological Survey (Project # 2008MD171B). The opinions and findings expressed in this paper are those of the authors and not of the National Science Foundation.

Williams DD, Williams NE, Cao Y (1999) Road salt contamination of groundwater in a major metropolitan area and development of a biological index to monitor its impact. Water Res 34(1):127–138CrossRefGoogle Scholar